Process and apparatus for the continuous pneumatic treatment of fine material

ABSTRACT

At least two separate zones in the bottom of a mixing chamber are supplied alternately with finely divided streams of agitating air, and fine material to be treated is supplied at alternate points in the top of the chamber, each of such points being located above one of such separate zones. The fine material is withdrawn at the bottom of the chamber. The point at which fine material is supplied is always a point at which the fine material in the chamber is relatively quiet, located above a zone in which the agitation of the material by air is relatively slight.

United States Patent Klein et al.

115; 3,656,717 1451 Apr. 18,1972

1541 PROCESS AND APPARATUS FOR THE CONTINUOUSPNEUMATIC TREATMENT OF FINE MATERIAL Hans Klein, Bergisch Gladbach; Wolfgang Kluger, Ennigerloh, both of Germany Polysius AG, Neubeckum, Germany July 6,1970

Inventors:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Aug. 28, 1969 Germany ..P 19 43 782.2

US. Cl ..259/4, 259/147, 259/151, 259/DIG. 17

Int. Cl ..B01f 13/02, 13011 15/02 Field of Search ..259/4, 18, 36, DIG. 17, 147, 259/151, 161; 34/10, 22, 57 A, 168, 169, 170, 174

References Cited UNITED STATES PATENTS 2,292,897 8/1942 Nielsen ..259/99 1,971,852 8/1934 Goebels" ..259/4 3,003,752 10/1961 Frost ..259/DIG. 17

FOREIGN PATENTS OR APPLICATIONS 543,647 12/1955 Belgium ..259/D1G. 17

Primary Examiner-Walter A. Scheel Assistant Examiner--Alan l. Cantor AttorneyMarshall & Yeasting [57] ABSTRACT At least two separate zones in the bottom of a mixing chamber are supplied alternately with finely divided streams of agitating air, and fine material to be treated is supplied at alternate points in the top of the chamber, each of such points being located above one of such separate zones. The fine material is withdrawn at the bottom of the chamber. The point at which fine material is supplied is always a point at which the fine material in the chamber is relatively quiet, located above a zone in which the agitation of the material by air is relatively slight.

7 Claims, 2 Drawing Figures PROCESS AND APPARATUS FOR THE CONTINUOUS PNEUMATIC TREATMENT OF FINE MATERIAL BACKGROUND OF THE INVENTION This invention relates to a method for the continuous pneumatic treatment of fine material, especially for the pneumatic mixing and homogenization of fine material which is continuously fed into a treatment space from above and continuously removed from this treatment space, wherein finely divided streams of air are supplied to the treatment space from below.

The invention also relates to a device for carrying out this method.

Methods of the above type are known wherein the material flows continuously into the treatment space through an inlet aperture. The treatment space is always to a great extent filled with material which is maintained in continuous mixing and homogenizing motion. Since the material in the treatment space and the new material flowing in usually have different densities, it very often happens in practice that the newly introduced fine material flows through the material already in the treatment space and is removed therefrom without any intensive mixture or homogenization having taken place.

A further disadvantage of this known method is that the entire quantity of material in the treatment space must be continuously pneumatically moved. Consequently a relatively large amount of air must be introduced into the treatment space from below, which involves an undesirably high energy consumption.

SUMMARY OF THE INVENTION The object of the invention is therefore to provide improvements in a method of the type described in such manner that while continuous operation with relatively low energy consumption is assured, there is very intensive pneumatic treatment, and in particular the said flowing through of new material is prevented.

According to the invention, this object is achieved in that at least two cross-sectional zones of the treatment space are alternately supplied with air at difiering rates in a manner known per se, and in that the material freshly fed into the treatment space is supplied to the cross-sectional zones which at any time are being supplied with little or no air.

Methods are already known in another connection wherein fine material is discontinuously mixed or homogenized by pneumatic means, with air supplied in different amounts to individual cross-sectional zones in mutually alternating sequence. In these cases, however, the freshly supplied material is fed into the treatment space through a single inlet aperture which during filling is continuously loaded with material. In order to achieve adequate mixing or homogenization, the treatment space must in this case be closed for the duration of the pneumatic treatment. With this known method continuous operation is thus impossible without the initially mentioned disadvantage of the unmixed fine material flowing through. A further disadvantage of this known method lies in the large number of treatment spaces (containers) needed to operate in parallel to produce an adequate output.

With the method in accordance with the invention, however, the freshly added material is always fed to a cross-sectional zone to which little or no air is being supplied. It therefore meets material which has already been treated and has been at rest for a short period, having roughly the same density as the freshly added material. It is therefore not possible for this new material to flow through the material present in the treatment chamber. When the cross-sectional zone filled up with fresh material is then supplied with more air after a predetermined period, another zone to which little or no air is being supplied can be filled up, while in the first-mentioned zone the newly supplied upper layer of material can be unifonnly distributed in the material already present, by the pneumatic treatment. In this manner a particularly intensive admixture or homogenization of the material is achieved, while the supply of large amounts of air to one zone only in volves a proportionately less consumption of energy.

As compared with the known discontinuously operating method, the method in accordance with the invention is also characterized by needing less space to achieve a given output.

With an apparatus as provided by the invention having more than two pairs of diametrically opposite cross-sectional zones distributed around the periphery of the treatment space and supplied with air at alternately varying rates, it is especially advantageous if at any time only one pair of cross-sectional zones is strongly fed with air, and the freshly fed material is supplied to a pair of weakly aerated zones which are offset as far as possible, preferably by from the strongly aerated pair. This insures that the freshly fed material is always fed to a pair of cross-sectional zones wherein the material has slowed down in movement to a minimum and has thus become dense.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section (on the line I-I of FIG. 2) through a device for carrying out the method of the invention.

FIG. 2 is a plan view of the device of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawings show a silo 1 forming a treatment space, used in this case for the continuous pneumatic mixing or homogenization of ground cement. The base 2 of this silo is provided with an air-permeable porous sheet 3 of funnel shape and divided into 12 sectors 4-15. Each of these sectors forms the lower wall of a cross-sectional zone. The sectors are connected by tubular conduits (e.g. l6, 17) to a common source of compressed air. At any moment two diametrically opposite sectors (e.g. 4 and 10, 5 and 11) are being supplied with-air, and may for instance be connected to an automatic timing device 50,50a, shown diagrammatically in FIG. 2, so that the individual pairs are alternately supplied with different amounts of air in clockwise sequence. A central outlet 18 is also provided in the base 2. As shown in this example, the funnel-shaped porous sheet 3 may have a more sharply inclined surface 3' in the peripheral region to aid movement of the material.

Twelve inlet apertures 20-31 are provided in the roof 19 of silo 1; each inlet aperture (e.g. 20) is precisely above the cross-sectional zone pertaining to one air supply sector (e.g. 4). Each inlet aperture is connected to a joining conduit comprising a pneumatic feed channel 32-43, terminating in a central inlet pipe 44 provided above the silo roof 19. The feed channels 32-43 can be controlled as indicated diagrammatically at 51,51a, so that at any time 'only two diametrically opposite channels (e.g. 35, 41) are feeding material to their corresponding inlet apertures (e.g. 23, 29). The controls 50 and 51 are operated simultaneously and synchronously as shown at 52. Consequently material is supplied to the two inlet apertures (e.g. 23, 29) corresponding to cross-sectional zones whose aeration sectors (e.g. 7, 13) are offset by 90 from the pair of sectors (e.g. 4, 10) which are then being strongly supplied with air.

The mode of operation of the device is as follows:

Fluidizing air is fed through selected tubular conduits (e.g. 16, 17) and the porous sheet 3, 3 to the silo 1 which is filled to a major extent with material to be mixed or homogenized. However, only one pair of sectors (e.g. 4, 10) are strongly supplied with air, while all the other pairs of sectors are only supplied with enough air to prevent clogging of the porous sheet, or to maintain a relatively thin lower layer of material in motion. The material in the strongly aerated cross-sectional zones is thus intensively mixed or homogenized, and moves into the adjacent cross-sectional zones (e.g. 5, 9, ll, 15). The material located in the cross-sectional zones above the sectors (e.g. 6, 7, 8, 12, 13, 14) which are farther offset at the periphery from the pair of sectors (e.g. 4, 10) being strongly aerated, can slow down in its motion, settle and therefore densify. Fresh material is then supplied through the corresponding inlet apertures (e.g. 23, 29) to the cross-sectional zones (e.g. 7, 13) which are offset by the greatest extent, i.e. by 90. This newly supplied material and the settled material have approximately the same density, so that the new material is deposited in a layer on the settled material in the corresponding cross-sectional zones. It is thus impossible for the freshly arriving material to flow through. At the same time as fresh material is being supplied, approximately the same amount of mixed or homogenized material flows through the outlet 18. This departing material stems in general from the cross-sectional zones whose corresponding pair of sectors (e.g. 4, 10) are being strongly aerated. Consequently only material is removed which has been effectively mixed or homogenized.

The process thus described in the two pairs of cross-sectional zones corresponding to the strongly aerated sectors (4, 10, broken shading) and the material-supplying inlet apertures (23, 29, full shading) now runs in cyclic succession through the entire cross-section of the container, as indicated in FIG. 2. Thus if the controls 50,51,52 are acting clockwise, the next sectors and 11 will be strongly aerated, and the material will be supplied through inlet apertures 24 and 30.

We claim:

l. A process for the continuous pneumatic treatment of fine material in a mixing chamber, comprising the steps of supplying at least two separate zones in the bottom of the chamber alternately with finely divided streams of agitating air, supplying fine material to be treated at alternate points in the top of the chamber, each of such points being located above one of such separate zones, and withdrawing the fine material at the bottom of the chamber, the point at which fine material is supplied always being a point at which the fine material in the chamber is relatively quiet, located above a zone in which the agitation of the material by air is relatively slight.

2. A process according to claim 1 wherein at least two pairs of zones in the bottom of the chamber are alternately supplied with finely divided streams of agitating air, the two zones of each pair being diametrically opposite and being simultaneously supplied with agitating air, and fine material always being supplied simultaneously at two diametrically opposite points in the top of the chamber located above zones in which the agitation of the material by air is relatively slight.

3. A process according to claim 2 wherein more than two pairs of zones in the bottom of the chamber are supplied in succession with finely divided streams of agitating air, the two points in the top of the chamber at which fine material is supplied always being spaced approximately from the two zones which are being supplied with agitating air.

4. Apparatus for the continuous pneumatic treatment of fine material, comprising a mixing chamber having a porous bottom, at least two air inlets arranged to supply agitating air to the chamber through separate zones in the porous bottom, a separate inlet for supplying fine material to the chamber, located in the top of the chamber above each such zone, an outlet for withdrawing fine material at the bottom of the chamber, a conduit for supplying compressed air to each air inlet, a separately controllable branch conduit feed channel for supplying fine material to each material inlet, and cyclicly operating controls, comprising an automatic timing device, for controlling in synchronism the flow of air through the conduits and the flow of material through the pneumatic feed channels to cause the fine material to be supplied to each zone only while that zone is being supplied with little or no air.

5. Apparatus according toclaim 8 comprising a central inlet pipe above the chamber connected to said branch conduits for supplying fine material to the chamber.

6. Apparatus according to claim 5 wherein each of the branch conduits comprises a pneumatic feed channel.

7. Apparatus according to claim 8 wherein the outlet for withdrawing fine material is located centrally in the porous bottom of the chamber. 

1. A process for the continuous pneumatic treatment of fine material in a mixing chamber, comprising the steps of supplying at least two separate zones in the bottom of the chamber alternately with finely divided streams of agitating air, supplying fine material to be treated at alternate points in the top of the chamber, each of such points being located above one of such separate zones, and withdrawing the fine material at the bottom of the chamber, the point at which fine material is supplied always being a point at which the fine material in the chamber is relatively quiet, located above a zone in which the agitation of the material by air is relatively slight.
 2. A process according to claim 1 wherein at least two pairs of zones in the bottom of the chamber are alternately supplied with finely divided streams of agitating air, the two zones of each pair being diametrically opposite and being simultaneously supplied with agitating air, and fine material always being supplied simultaneously at two diametrically opposite points in the top of the chamber located above zones in which the agitation of the material by air is relatively slight.
 3. A process according to claim 2 wherein more than two pairs of zones in the bottom of the chamber are supplied in succession with finely divided streams of agitating air, the two points in the top of the chamber at which fine material is supplieD always being spaced approximately 90* from the two zones which are being supplied with agitating air.
 4. Apparatus for the continuous pneumatic treatment of fine material, comprising a mixing chamber having a porous bottom, at least two air inlets arranged to supply agitating air to the chamber through separate zones in the porous bottom, a separate inlet for supplying fine material to the chamber, located in the top of the chamber above each such zone, an outlet for withdrawing fine material at the bottom of the chamber, a conduit for supplying compressed air to each air inlet, a separately controllable branch conduit feed channel for supplying fine material to each material inlet, and cyclicly operating controls, comprising an automatic timing device, for controlling in synchronism the flow of air through the conduits and the flow of material through the pneumatic feed channels to cause the fine material to be supplied to each zone only while that zone is being supplied with little or no air.
 5. Apparatus according to claim 8 comprising a central inlet pipe above the chamber connected to said branch conduits for supplying fine material to the chamber.
 6. Apparatus according to claim 5 wherein each of the branch conduits comprises a pneumatic feed channel.
 7. Apparatus according to claim 8 wherein the outlet for withdrawing fine material is located centrally in the porous bottom of the chamber. 